Rectilinear-motion driving device for voice coil motor

Abstract

A linear-motion driving device includes a movable shaft, a gas bearing for supporting the movable shaft, a housing for supporting the gas bearing, and a motor having a voice coil for displacing the movable shaft. The bearing housing is disposed inside the voice coil.

What is claimed is: 
     
       1. A linear-motion driving device, comprising: a movable member;   a gas bearing having a pad for supporting said movable member;   a motor having a voice coil for displacing said movable member along a predetermined axial direction, wherein said voice coil is formed as a unit with said movable member and wherein said pad and said movable member are disposed inside said voice coil; and   a mechanism for limiting rotational motion of said movable member about said axial direction, wherein said limiting mechanism includes a guide plate formed as a unit with said movable member and disposed outside said voice coil, and wherein said limiting mechanism limits the rotational motion of said movable member by using said guide plate and static gas pressure.   
     
     
       2. A device according to claim 1, wherein said pad and said voice coil are disposed concentrically. 
     
     
       3. A linear-motion driving device, comprising: a movable shaft;   a bearing housing having a longitudinal bore through which said movable shaft extends;   first and second gas bearing means provided at opposite ends of said bearing housing, respectively, for supporting said movable shaft relative to said bearing housing with use of static gas pressure;   a motor for moving said movable shaft relative to said bearing housing along an axial direction, said motor having a motor housing for covering said bearing housing, a magnet attached to said motor housing and a voice coil fixed to an end portion of said movable shaft by a fixed plate, wherein said voice coil is disposed inside said motor housing and extends in a direction covering said movable shaft; and   a mechanism for limiting rotational motion of said movable shaft, said limiting means having a guide plate attached to said end portion of said movable shaft to which said voice coil is fixed.   
     
     
       4. A device according to claim 3, wherein said limiting mechanism has a guide block for discharging pressurized air to opposite sides of said guide plate. 
     
     
       5. A device according to claim 3, wherein said bearing housing is formed with a discharge port through which a portion of air passing through one of said first and second gas bearing means and serving to support said movable shaft by static pressure is discharged outwardly through said bearing housing. 
     
     
       6. A device according to claim 5, wherein each of said first and second bearing means has a porous material gas bearing member of ring-like shape. 
     
     
       7. A device according to claim 3, wherein said magnet is provided inside said motor housing. 
     
     
       8. A device according to claim 7, wherein said motor housing extends so as to accommodate therein at least a portion of said bearing housing. 
     
     
       9. A device according to claim 3, further comprising a linear encoder for controlling movement of said movable shaft and having a scale attached to said end portion of said movable shaft to which said voice coil is fixed.